Although dehydration is commonly viewed as a condition affecting athletes and manual laborers, dehydration is a health concern for all individuals. Dehydration is especially a concern in places where individuals are susceptible to developing a fluid imbalance and/or thermoregulatory challenge, like for example, in senior centers, public schools, hospitals and national parks.
The hypothalamus inside the brain monitors body temperature, and when heat begins to accumulate, certain physiological adjustments are made to maintain a healthy body temperature. Regulation of body temperature is accomplished in a variety of ways including radiation, convection, conduction and evaporation through sweating. Evaporation is a primary mode of heat transfer during physical exertion and can account for up to 80% of the body's heat loss. In extremely hot conditions, the human body can lose as much as 2 liters of sweat per hour. If the body's water supply is not replenished continuously, dehydration might occur. In some cases, this can result in dangerous and potentially life-threatening consequences.
A variety of factors affect an individual's sweat rate. These factors include the ambient temperature and humidity, the intensity and duration of the physical exertion, the type of clothing worn by the individual, the individual's fitness level, hereditary factors, and additionally the individual's state of acclimatization and current hydration status. Early warning signs that an individual is entering a state of dehydration include: irritability, vomiting, thirst, headache, dizziness, fatigue, chills and darker urine than normal. If allowed to persist, dehydration can lead to muscle cramps, excessive sweating, heat exhaustion and possibly heat stroke.
An individual's desire to consume fluids (i.e., thirst) is oftentimes not an accurate means by which to gauge the individual's hydration level. The hypothalamus monitors the body's temperature and controls the physiological response to a thermoregulatory challenge. The hypothalamus is affected by sodium levels, blood osmolality and overall plasma volume. The mechanisms for controlling body temperature are hormonal, physiological, metabolic and behavioral. All of these factors are subject to individual variation, and therefore it can be difficult to predict the exact amount of fluid an individual should consume to avoid dehydration.
Clinical methods to monitor and diagnose dehydration include tests based on plasma osmolality, urine specific gravity, urine osmolality and various isotope techniques. Field methods for diagnosing dehydration are generally less accurate than clinical methods, but nonetheless provide valuable indicators of dehydration. Field methods include monitoring acute weight loss (e.g., pre-practice vs. post-practice weight), urine color and other typical signs of dehydration (e.g., thirst, dizziness, headache, irritability etc.).
Urine color can be used to assess an individual's hydration level because urine color may change in response to changes in the individual's overall hydration level. A euhydrated individual typically produces urine which is light yellow or straw color. A dehydrated individual produces urine that is dark yellow, orange, gold, light brown or brownish-green. When the body enters a state of dehydration, there is a deficit between fluid intake and fluid loss. This deficit is reflected by an increased concentration of particulates excreted in the urine. If more water is lost through sweating than is consumed through drinking, less water is available to dilute the particulates in the urine, and so the urine color becomes darker.
Known color scales for analyzing urine color are printed on a paper chart. An individual must collect his or her urine in a clear container, and then hold the paper chart next to the urine sample to make the color comparison. Individuals oftentimes object to the collection and handling of urine that is required to obtain an accurate measurement. This process is also time consuming in that the urine must first be collected in the clear container, and subsequently compared to the paper chart. Because known color scales require the collection of urine, these color scales are not helpful to an individual who excretes his or her urine into a urinal or toilet. A need therefore exists for a quicker and less burdensome manner of analyzing urine color.